• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.7
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• pp.70-75
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• 2005

In this study, experimental investigations were conducted on NOx emission characteristics with fuel swirl flow in swirl combustor. Many types of vanes, which altered air and fuel swirl angles, were employed to verify the mixing processes. For strong air swirl, fuel counter-swirl resulted in relatively large turbulent intensity, high energy to the high frequency region and narrow width of high temperature region compared with co-swirl condition. These effects of fuel counter-swirl resulted in low NOx emission characteristics at strong air swirl condition. And NOx reduction mechanism was also discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.85-91
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• 2003

In this study, the potential possibility of oxygenated fuel such as Methyl tertiary butyl ether (MTBE) was investigated for the sake of exhausted smoke reduction from diesel engine. MTBE has been used as a fuel additive blended into unleaded gasoline to improve octane number, but the study of application for diesel engine was incomplete. Because MTBE includes oxygen content approximately 18%, it is a kind of oxygenated fuel that the smoke emission of MTBE is reduced remarkably compared with commercial diesel fuel. But, the NOx emission of MTBE blended fuel is increased compared with commercial diesel fuel. And, it was tried to analyze not only total hydrocarbon but individual hydrocarbon components from $C_1$ to $C_6$ in exhaust gas using gas chromatography to seek the reason for remarkable reduction of smoke emission. Individual hydrocarbons($C_1$~$C_6$) as well as total hydrocarbon of oxygenated fuel are reduced remarkably compared with diesel fuel. And, the effects of exhaust gas recirculation(EGR) on the characteristics of NOx emission has been investigated, too. It was found that simultaneous reduction of smoke and NOx was achieved with oxygenated fuel and cooled EGR method.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.448-453
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• 2003

In this study, the effects of oxygen component in fuel and exhaust gas recirculation(EGR) method on the exhaust emissions has been investigated for a D.I. diesel engine. It was tested to estimate change of exhaust emission characteristics for the commercial diesel fuel and oxygenate blended fuel which has five kinds of blending ratio. Dimethoxy methane(DMM) contains oxygen component 42.5% in itself. and it is a kind of effective oxygenated fuel for reduction of smoke emission. It was affirmed that smoke emission was decreased with increasing of DMM blending ratio. But, NOx emission was increased compared with commercial diesel fuel. It was needed a NOx reduction countermeasure that EGR method was used as a countermeasure for NOx reduction. It was found that simultaneous reduction of smoke and NOx emission was achieved with DMM blended fuel and cooled EGR method($10{\sim}15%$).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.283-290
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• 2010

The main goal of this study is to examine the use of a hybrid -fuel lean reburning system with air staging for $NO_X$ reduction. The experimental variables include the reburn fuel fraction, sizes of reburn- fuel-injection nozzles, oxygen enrichment ratio, and location of reburn- fuel- injection. The effect of the flow field induced by air- staging combustion on $NO_X$ reduction is considered, and then, the $NO_X$ reduction rate is compared with only fuel lean reburning system. On the basis of the effectiveness of each De-$NO_X$ process, the advantage of using the hybrid reburning system with air staging is determined and discussed.

• Environmental Engineering Research
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• v.11 no.3
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• pp.149-155
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• 2006

NOx reduction experiments were conducted by direct injection of urea into a diesel fueled, combustion-driven flow reactor which simulated a single engine cylinder ($966cm^3$). NOx reduction tests were carried out over a wide range of air/fuel ratios (A/F=20-40) using an initial NOx level of 530ppm, and for normalized stoichiometric ratios of reductant to NOx (NSR) of 1.5 to 4.0. The results show that effective NOx reduction with urea occurred over an injection temperature range of 1100 to 1350K. NOx reduction increased with increasing NSR values, and about a 40%-60% reduction of NOx was achieved with NSR=1.5-4.0. Most of the NOx reduction occurred within the cylinder and head section (residence time <40msec), since temperatures in the exhaust pipe were too low for additional NOx reduction. Relatively low NOx reduction is believed to be due to the existence of higher levels of CO and unburned hydrocarbons (UHC)inside the cylinder, and large temperature drops along the reactor. Injection of secondary combustible additives (diesel fuel/$C_2H_6$) into the exhaust pipe promoted further substantial NOx reduction (5%-30%) without shifting the temperature windows. Diesel fuel was found to enhance NOx reduction more than $C_2H_6$, and finally practical implications are further discussed.

• Journal of ILASS-Korea
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• v.7 no.1
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• pp.7-13
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• 2002

This paper is study on simultaneous reduction of NOx and soot for direct injection diesel engine using high and low cetane fuels. The stratified injection system was applied for diesel engine to use high and low cetane fuel. In this study, diesel fuel was used as high cetane fuels, methanol was used as low cetane fuels. Some parts of the injection system, ie. Nozzle holder. delivery vale, was remodeled to inject dual fuel sequentially from one injector. The leak injection quantity ratio of dual fuel was certificated by volumetric ratio at injection quantity experiment. According as concentration of low cetane fuel was varied, combustion experiment was performed using Toroidal and Complex chamber. Also, exhaust gas and fuel consumption were measured at the same time. Simultaneous reduction of NOx and soot was achieved at complex chamber regardless of concentration of low cetane fuel. However, according as concentration of low cetane fuel was increased, THC and CO was increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.150-155
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• 2012

Lean NOx Trap (LNT) catalysts are capable of reducing exhaust NOx emissions from diesel engines. LNT stores NOx in lean condition and exhausts N2 by reducing NOx in rich condition. NOx reduction characteristic of LNT catalysts using throttle position sensor and fuel injection timing control for light-duty diesel engine was investigated. In contrast to SCR system, LNT catalyst uses diesel fuel in resuctant. Also if the concentration of reductant is exceeded, excessive amount of reductant will slip throughout LNT and cause another emission problem. Thus LNT regeneration with precise engine control established that can make higher NOx conversion efficiency and lower fuel penalty, prevent another emission problem. NOx and reductant concentration were measured by the NOx sensor and Mexa7100D equipped inlet and outlet of catalyst. As a result of engine test, regeneration strategy has reached high of 77.8% NOx conversion efficiency according to engine operation condition. Moreover, we have proved that it is possible to use regeneration strategy of LNT within 5% fuel penalty.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.76-88
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• 1995

The effects of exhaust gas recirculation(EGR) on the characteristics of NOx emissions and specific fuel consumption rate have been investigated using an eight-cylinder. four cycle. direct injection diesel engine operating at several loads and speeds. The theoretical NO formation concentration is calculated with the equivalence ratio as a parameter of flame temperature to study the effect of EGR on NOx emissions in the diesel combustion. The experiments in this study are conducted on the fixed fuel injection timing of $38^{\circ}$ BTDC regardless of experimental conditions. It is found that the specific fuel consumption rate is slightly increased with EGR rate. and NOx emissions are markedly reduced owing to the drop of the incoming oxygen concentratio and the increase of equivalence ratio as the EGR rate increases.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.47-56
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• 2001

Nitrogen oxides(NOx) and smoke emissions of diesel engine are regarded as a source of air pollution, and there is a global trend to enforce more stringent regulations on these exhaust gas emissions. However, the trade-off relation of NOx and smoke is a main obstacle to reduce both of them simultaneously. In this paper, experiments were conducted with an oxygenated fuel(diethyl ether) as an effective way to improve the trade-off relation of NOx and smoke. Exhaust emissions of diesel fuels with DEE were influenced by the additive content of DEE and the injection timing. Especially, DEE effected more at the high engine speed and load than at the low engine speed and load. Diesel fuel blended with DEE 10% was a desirable blend for the simultaneous reduction of NOx and smoke.

• Journal of the Korean Society of Combustion
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• v.14 no.1
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• pp.19-24
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• 2009

A novel low NOx oil burner of 0.7 MW (for a 1 ton steam/hr industrial boiler) was designed and tested to investigate the combustion characteristics through in-flame measurement and flue gas analysis. Flame shape was observed by CCD camera and $CH^*/{C_2}^*$ radical distribution in the flame were observed, along with measurement of flue gas composition such as NOx and CO, for various heat inputs, excess airs and pressure of the fuel spary nozzles. The flame showed the two-zone structure: fuel-rich and fuel-lean zone, which was very favorable for the low-NOx combustion, and the NOx emission for haevy oil combustion was significantly reduced to < 150 ppm at 4 % $O_2$, compared with the NOx level of a conventional heavy oil burner.